Bug 105349
| Summary: | With an SMP kernel NUMA should be enabled for increased memory performance | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 3 | Reporter: | Albert Fluegel <tdsc.af> |
| Component: | kernel | Assignee: | Arjan van de Ven <arjanv> |
| Status: | CLOSED NOTABUG | QA Contact: | David Lawrence <dkl> |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | 3.0 | ||
| Target Milestone: | --- | ||
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2003-09-26 08:09:40 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
the kernel cannot be built with NUMA support turned on. Reason is a loop in #includes. First, the asm/mmzone.h needs a definition from linux/mmzone.h . Including linuz/mmzone.h before asm/mmzone.h leads to an error because some wait_q_type is not defined. Reason is, that mmzone.h and wait.h include each other. I wonder what the IBM person bases this on, especially since 1) Opteron systems hardly are NUMA 2) The kernel by default (including ours) does not have a lot of NUMA support (some other linux distros patch in a lot of this, which slows down the normal case. gaining 30% relative to that is easier of course :) AFAIK Opteron SMP systems are NUMA by design. Each part of the memory is assigned to a CPU. When a CPU wants to access memory, that is assigned to the other CPU, the access passes the memory controller of the other CPU, what makes the access slower than a local one. I really would like to benchmark this, but as explained i don't get the kernel built due to type definition problems :-( They are NUMA, however the NUMA factor is very very close to 1 (unlike some other boxes where the NUMA speed is in the order of 15); academic research has shown that a numa factor of 2 is about the turnover point for the OS doing special NUMA hacks. A performance improvement of 30% is certainly believable for systems with a large NUMA factor (like the IBM x440) but I have a hard time believing it for real world use on AMD Opteron machines. |
Description of problem: Not a problem, but a feature request. Some guy from IBM stated, that with NUMA enabled on an Opteron SMP system memory performance is sped up by up to 30%. Please set CONFIG_K8_NUMA=y CONFIG_ACPI_NUMA=y in /usr/src/redhat/SOURCES/kernel-2.4.21-x86_64-smp.config Version-Release number of selected component (if applicable): 2.4.21-1.1931.2.393 How reproducible: N/A Steps to Reproduce: 1. 2. 3. Actual results: Expected results: Additional info: